1. Field of the Invention
The present invention relates to a gas/liquid separation system for blow-by gas.
2. Description of the Related Art
A cyclone case 70 and a PCV valve 72 shown in FIG. 7 are used as a system for returning blow-by gas leaking from a combustion chamber in an automobile to an air intake system to allow the gas to be reburned inside the combustion chamber. The cyclone case 70 is a device that separates the blow-by gas leaking from the combustion chamber into gas and oil.
The PCV valve 72 is a device that regulates the flow volume of the gas and returns the gas to the air intake system, and a valve is slidably accommodated inside a PCV valve housing 72A.
However, because the cyclone case 70 and the PCV valve 72 are separate parts, the cyclone case 70 and the PCV valve 72 must be connected. As methods for this connection, a method (not illustrated) in which the cyclone case and the PCV valve are connected by a hose and a method in which bosses 74 are disposed at the cyclone case 70, with the PCV valve housing 72A being fitted thereto, have been adopted.
However, in the structure in which the PCV valve housing 72A is fitted to the bosses 74 of the cyclone case 70, the welding process becomes complicated because there are two bosses 74 to which the PCV valve housing 72A is fitted, and gas leakage cannot be completely suppressed if there are no seal members such as O-rings 73 because the PCV valve housing 72A is fitted to the bosses 74. Moreover, the size of the overall system becomes larger in order to connect several parts.
In consideration of the above-described facts, it is an object of the present invention to provide a gas/liquid separation system in which a process by which a cyclone case and a PCV valve are welded is reduced, in which a sealing property at an outflow portion that returns gas to an air intake system can be secured, and in which the overall structure is compact.
A gas/liquid separation system of an aspect of the invention is a gas/liquid separation system, comprising: a cyclone case including a cavity having an opening at an upper portion thereof, the cyclone case causing gas that is introduced to the cavity and includes oil mist to be circulated along a surface of the cavity and separating the gas into gas and oil; a gas outflow pipe including a flange that blocks the opening and a pipe that passes through the flange and allows the gas to circulate to the outside of the cavity; and a housing including a valve that adjusts the flow volume of the gas flowing out from the pipe, with the housing being welded to a peripheral edge portion of the upper opening of the cyclone case so as to accommodate the valve and cover the flange, and allowing the gas that has flowed out from the pipe to flow to the outside of the system.
The gas that is introduced to the cavity is blow-by gas leaking from a combustion chamber in an automobile. According to the gas/liquid separation system of the aspect of the invention, when the blow-by gas is introduced to a cylindrical portion of the cyclone case, the blow-by gas is made to gyrate inside the cyclone case and is separated into gas and oil. The gas flows out to the gas pipe of the gas outflow pipe, and the flow volume of the gas flowing to an air intake system is adjusted by the valve.
The upper opening of the cylindrical portion of the cyclone case is blocked off by the flange of the gas outflow pipe, and the housing in which the valve is accommodated is welded to the upper opening edge portion of the cyclone case. In this manner, the cyclone case and the housing can be welded in a state in the cyclone case and the housing are joined together, with the upper opening edge portion of the cyclone case, and not a periphery of the gas pipe, serving as the portion at which the cyclone case and the housing are welded. Thus, the sealing property can be secured without using seal members, and one portion can serve as the welding portion.
In the aspect of the invention, the cyclone case may have an annular shape suited for fitting at the edge portion of the opening, and the housing may have a shape that can be fitted together with the annular shape at a position facing the annular shape and may be fitted together with the cyclone case. The invention can be also configured so that the flange further has a shape that can be fitted together with the annular shape at a position facing the annular shape of the cyclone case, so that the housing and the flange fit together with the cyclone case.
That is, in the aspect, an annular fitting portion is formed at the upper opening edge portion of the cyclone case, and an annular fitted portion that fits together with this annular fitting portion is formed at the flange and at the housing.
By configuring the invention as described above, the annular fitted portions formed at the flange of the gas outflow pipe and at the housing are fitted together with the annular fitting portion formed at the upper opening edge portion of the cyclone case. Thus, three partsxe2x80x94the housing accommodating the valve, the cyclone case, and the gas outflow pipexe2x80x94can be simultaneously welded.
The invention can also be configured so that the cyclone case includes an annular step portion formed at an inner wall near the opening and the flange includes an outer peripheral wall, with an annular rib being included at an upper edge thereof, so that the annular step portion and the annular rib engage.
The annular rib formed at the outer peripheral portion of the flange of the gas outflow pipe engages with the step portion formed at the inner wall of the cyclone case, and the gas outflow pipe is sandwiched between the cyclone case and the housing. Thus, welding of the gas outflow pipe can be omitted.